The suppression or elimination of odors, particularly undesirable odors, has been the objective of untold investigations over the period of many centuries. In general these investigations have been focused on either of two approaches, namely (a) odor masking, in which a substance of strong yet relatively pleasant odor is introduced into the proximity of a less pleasant odor source with the intent of overburdening the olfactory receptors with the dominant pleasant odor, or (b) sequestering the undesired odorous substance in a non-volatile form either by chemical reaction, adsorption or absorption on a sorbent material exhibiting a sorptive preference for the odorous substance.
With respect to the latter approach, a very significant advance has been described in detail in U.S. Pat. No. 4,795,482, Gioffre et al, the entire disclosure of which is incorporated by reference herein. The discovery which is the basis for this advance is that a particular subclass of crystalline zeolitic molecular, i.e., those in which at least 90 percent of the framework tetrahedral oxide units are SiO.sub.2 tetrahedra and have a sorptive capacity for water, at 25.degree. C. and 4.6 torr, of less than 10 weight percent, possess a remarkable capability to sequester vapor phase molecules of odorous organic materials. In some instances, the zeolitic materials are found to render odorless vapors phases in which concentrations of the odor-causing composition must be reduced to levels below 0.00000004 mg./liter, the threshold concentration for detection by the normal human olfactory system. It is apparent that much more than mere organophilic adsorptive selectivity is involved. Although the phenomenon is not fully understood at present, one theory is that a catalytic process is involved whereby the odor molecules are reacted inter se or with other available molecular species, such as oxygen, to form compounds or polymers which no longer stimulate the olfactory receptors. It is known that high molecular weight organic molecules are significantly less odorous than low molecular weight molecules of similar atomic content and structure, n-decyl and lauryl mercaptans have no more odor than their corresponding alcohols. Thus, polymerization or condensation reactions could be beneficial in the present process. It is another possibility that the adsorption isotherms for the odor molecules for the very highly siliceous zeolite adsorbents involved here have steeper slopes in the region of very low adsorbate partial pressures than has heretofore been appreciated. Since the partial pressures of odor molecules often encountered are frequently quite low, the high silica adsorbents would exhibit superior adsorptive performance for that reason. Still another factor may be van der Waals interactions between the odor molecules and the molecular sieve causing the odor molecules to be tightly bound and trapped within the adsorbent. There may also be a coadsorption of two or more different odor molecules resulting in a synergism that eliminates the odors of both.
The crystalline zeolitic adsorbents, to be effective in the elimination or suppression of odors, must in most instances be applied topically to the odor source. Such topical application can involve the use of powders, aerosol sprays, lotion formulations and the like. For these procedures the powderous nature of the very small crystallite forms in which zeolitic compositions are conventionally synthesized is ideally suited since further size reduction by grinding will ordinarily not be required. There are, however, a considerable number of applications for which powders are not completely satisfactory. For example, it has been proposed to utilize the deodorizing properties of high-silica molecular sieves in a variety of fibrous absorbent articles such as diapers, catamenial devices, wound dressings, incontinence pads, and shoe inserts. These articles are disclosed in detail in U.S. Pat. No. 4,826,497 (Marcus et al). It is important that the molecular sieves be incorporated into these articles in a manner whereby they not only remain in a dispersed condition throughout the fibrous area to which they are initially imparted, but also that their deodorizing properties are not unduly diminished as a consequence of the means used to prevent their dislocation. It is virtually impossible to prevent powdered solids such as molecular sieve crystallites from separating from fibrous batting without the use of some type of adhesive adjunct. Such adhesives necessarily cover at least a portion of the surface of the adsorbent particles and thereby tend to decrease their deodorizing capacity.
Another disadvantage of powders in general and molecular sieve powders in particular is the difficulty involved in the handling and dispensing operations carried out by the automated production apparatus used almost universally in the commercial scale manufacturing of articles which contain the powders. In addition to having the potential for creating harmful dust contamination of the air in the production area, the powders are difficult to transport and meter accurately and cause abrasive damage to machine parts in contact with the moving powder particles.